1. Field of the Invention
The present invention relates to a Wavelength Division Multiplexing (WDM) transmission system to perform optical transmission by multiplexing light signals having a plurality of wavelengths, and an optical fiber used as the optical transmission line for the WDM optical transmission system.
2. Related Background Arts
The WDM transmission system using an optical fiber network can transmit a large volume of information. The WDM transmission system comprises a transmitter to send out light signals having a plurality of wavelengths, an optical fiber to transmit these light signals, a receiver to receive these light signals, and an optical fiber amplifier to amplify these light signals. In order to increase the transmission capacity of the WDM transmission system, an attempt has been made to expand the wavelength band used for the transmission.
European Patent Application Publication No. EP 1037074 discloses an optical fiber that has appropriate chromatic dispersions in the whole range of wavelengths including 1.53 μm to 1.61 μm, in which the optical fiber amplifier can obtain a positive gain. The optical fiber can hence restrain the waveform degradation of the light signal due to a nonlinear optical phenomenon as well as the waveform degradation of the light signal due to the accumulation of the chromatic dispersions. The zero dispersion wavelength of this optical fiber is at least 1.61 μm but not more than 1.67 μm, and the chromatic dispersion slope at wavelength of 1.55 μm is 0.15 ps•nm−2•km−1 or less. In the implementation examples of the cited invention, optical fibers having a chromatic dispersion slope of at least 0.07 ps•nm−2•km−1 but not more than 0.15 ps•nm−2•km−1 are disclosed.
As for the optical fibers disclosed in the above-mentioned bulletin no consideration is made about the use in 1.31 μm band and 1.45 μm band (S band).